The present invention relates to a door structure for use in coke ovens, the structure being of the type having at least two locking head rails and a door body continuously made of a flexible and elastic material and being provided with a sealing membrane cooperating with compression elements which bias the sealing membrane against a door frame on the oven. In particular, the door structure of this invention is designed for operation with temperature gradients T of more than 100 K/m.
In the construction of modern coke oven installations, the trend is to design coke oven chambers which are larger in size in comparison with prior constructions and especially the height of the chambers tends to increase. While prior coke ovens were mainly built with chamber heights up to about 4 meters and chamber width up to about 450 mm, contemporary coke oven batteries have chambers up to 8 meters heigh and up to 600 mm wide, and these dimensioning has proved successful in operation. This development has contributed essentially for improving the economy of the coke production.
Due to the before described increased dimensions, an effective seal of the chambers in the region of the door structures is of particular importance in order to protect environment against pollution. Conventionally, the coke oven doors are pressed against door frames on the chambers by head rails, as a rule by two, but frequently by three locking head rails.
A large number of different door structures has been already developed and applied with a different degree of success. In general it can be stated that with increasing size of the openings of the coke oven chambers the construction and design of door structures which sealingly close the chambers during the entire coking process has become increasingly more difficult.
As known, the coke door structures has been equipped with most diversified forms of metal on metal sealing strips, such as angular membranes, Z-membranes, flat steel membranes, wedge-like sealing strips and the like. All these prior art sealing members, even if exhibiting over a certain range elastic quality and being assisted by pressure elements such as compression springs to insure proper contact with the door frame, must be readjusted from time to time depending on their dislocation or deformation caused by temperature differences acting on the chamber door frame and/or door bodies. This readjustment of flat or wedging membranes for example, is usually made by hammer blows, and in the case of elastic membranes the compression elements must be reset.
In practice it has been found that the before-mentioned prior art measures for sealing the doors are frequently insufficient especially for sealing chamber openings of large height and that frequently a contamination of the environment will result.
Depending on the construction of the coke oven, time intervals between 16 and 25 hours are required between the charging of a chamber with cold coal and the completion of the coking process. During this time period, both the chamber door frames and the door bodies are exposed to different temperature loads. The temperature loads produce again different temperature gradients in the door frames and door bodies which in turn cause different deformations during the coking period. Moreover, the deforming condition of the door frame and body is further influenced by ambient conditions, for example by heavy rain or large temperature variations. Also the exposure of the door frame to flame causes over prolongated time periods a change in the frame form.
Due to the temperature load the changed contour of the door body normally strongly deviates from the contour of the door frame and consequently over the entire height of the door a gap of variable width develops between the door body and the door frame. The width of the gap also changes with time.
The magnitude of the thermal deformation of the chamber door frames and the door bodies increases quadratically with the height of the chamber and consequently the gap between the frame and the door body changes in the same extent in width. It is evident therefore the problems encountered with sealing of the door structure become substantially aggravated with the increased height of the oven chamber.
Contemporary embodiments of door bodies, due to thermal loads are subject to considerable thermal deformations which at doors of a height of about 8 meters may amount to about 25 mm. In such door bodies which are usually made of heavy duty U-steel sections with web faces of a height of more than 250 mm, a counterdeformation by available locking forces exerted by the head rail is possible only to an extremely limited extent. The provision of mostly spring-loaded sealing membranes has the purpose of covering relatively large gaps between the door body and the door frame particularly in the top range, intermediate range and the bottom range of the door. In order to obtain the requisite bending elasticity, the membranes are normally made of metal sheets of minute thickness of maximum of 1.5 mm. The sealing sheet metals of such a small thickness however are hardly suitable for withstanding rough operational conditions of a coke oven and for withstanding the attack of mechanical cleaning tools. For this reason, the sealing means require considerable maintenance and cause dead times.
Compression springs acting on the sealing membranes must have a characteristic line which insures that at relatively long course or pitch of the spring sufficient compression force is still available in order to compensate for retroactive forces resulting from the flexture of the membrane; moreover the compression spring must exhibit sufficiently large contact pressure with specific sealing force q between a sealing edge and the chamber door frame at all operational conditions of the oven. This contact pressure should not fall below a certain minimum value during the entire coking time. This requirement, however, has not been met with conventional door structures.
In order to diminish the aforementioned difficulties it has been already devised to equip the door structures with door bodies having flexible and elastic quality. For example, in the German publication DE-PS No. 2,536,291 it has been proposed that above and below the door locking devices (head rails), the metal door body be provided with recesses which reduce the resistance and thus enable the fracture of the door body in its top and bottom regions. This measure, however, fell below expectation in the case of high oven structures.